NHOR-Landcruisin builds another Subaru

[Landcruisin60]

So I got the front part all welded up, all thats left is a harness bar, door bars and the rear diagonals and X. I'm getting low on 1.75in DOM so can I use 1.5in DOM for the harness bar and rear X? I'd still be using 1.75 for my door bars and diagonals from the top of the main hoop down to the strut mounts. I've seen people just make the main structure of the cage out of 1.75 and the X's and such out of 1.5, but I wanted to be sure that would fly for hill climbs.

[walterclark]

Our rules do not specifically permit this. This may be due to the simplified wording, or it may be deliberate.

I know the FIA rally rules permit 1.5" .095 be used beyond what it terms "basic structure", which includes most tubes other than the main 4 point cage. So my take would be yes that is reasonable, but I am not on the technical committee.

Someone like John R. or Don T. should be able to correctly answer this.

[Mopar 151]

Sorry about the delay - i was gonna ask Don at Burke, but hey, ya know.....
Anyway - as we state somewhere in the rules that we accept FIA (and SEMA) construction standards as adequate, I'm pretty sure it would fall under that.
And, IMHO, because of the shorter spans, etc in the areas in question, the material you are proposing to use there is quite adequate.
You mentioned before that this may be a "NEHA only" cage - if so, you are permitted to tie it to the car's structure as many places as you can - I would certainly do so at the top of the windshield, to the dashboard reinforcement in the unibody, to the OE shoulder harness mounts at the B pillar (look at Arlo's Pugeot for this one), the lower firewall/framerails, and the tops of all 4 strut towers. All of this is basically free speed, and will make the car last much longer under racing conditions.
Given the method you used for a roof bar reinforcement, you may wish to consider a bar in the center of the windshield (aka Earnhardt bar), tying the windshield header to the top center of the firewall, i.e., where one of these would bolt to:

An example from Troyer:

[Landcruisin60]

So I havent updated this recently because I've been busy and havent worked much on it...


But I'm getting pretty close, I think all thats left is a few gussets. I built a harness bar and door bars in the last couple days and finished welding in the foot plates last week.


Here are some pics.

[walterclark]

The harness bars join the hoop braces at the X junction.

I hope that based on having test fit the seats and ensuring the leadout angle of your harnesses from the seat openings to the middle of the bar was 0-20 degrees down.

We have run into a spate of harness bars positioned way too low for one reason or another.

[sachilles]

Walter, could you clarify that for me.

Rally america rules say that the shoulder belt should go from horizontal to 10 degrees below horizontal. However, their diagram makes a 90 degree angle from the seat back, and anything above that and below horizontal is in the OK range.

So my confusion is related to the seat back. Does the seat back orientation affect the acceptable harness angle? Or is it just based upon horizontal?


Thanks.

[Landcruisin60]

The harness bars join the hoop braces at the X junction.

I hope that based on having test fit the seats and ensuring the leadout angle of your harnesses from the seat openings to the middle of the bar was 0-20 degrees down.

We have run into a spate of harness bars positioned way too low for one reason or another.

The center of the bar is almost at the top of the openings, my shoulders are taller than the harness openings in the seat. My seat more or less sits on the ground.


What do people recommend about the node in main hoop? From what I gather people generally either use saddle gussets are tube with plate over it. My notcher cant notch a short enough piece of tube to make gussets between the harness bars and the X. The angles also arent 90s or 45s so it makes buying a premade saddle gusset difficult.

[walterclark]

Everyones rules need to be updated. The illustration in the RA rules is old. The text is accurate and reflects a change in thought based on the mandatory use of the H&NR - and the shoulder harness angle required by those, such as the Hans. The installation of the shoulder harness is changing as H&NR influences become mature and things like what happens to a seat and ones spine in a crash where the harnesses are too low finally sink in.

If you looks at in structions from many of the latest design harnesses like Schroth, they now mandate an angle of no greater than 20 degrees below horizontal and no less than 0 degrees.

This is a quote from their instructions at their web site http://www.schroth.com/installation-ins ... index.html:

Shoulder Belt Routing (applies to all restraint types)

· Shoulder belts must run from the shoulders horizontally or down, at no more than a 20° angle.

· In cases where the shoulder belts must be routed down to the chassis floor, support by a roll cage bar or harness guide at the appropriate height is essential to establish the horizontal shoulder strap routing off the shoulder/HANS®. Most racing seats are not designed and tested to carry shoulder belt crash loads from downward installation. Severe injury or death could result. A 45° downward shoulder belt installation is possible with seats that SCHROTH has positively tested to take a load measured during a 50 kph [31 mph] and 28 G impact with a 75 kg (175 lb) dummy. Refer to the list of SCHROTH approved racing seats in section “About Seats”. WARNING: 45° downward shoulder belt installation is not recommended with HANS®.

· For the best restraint of the occupant’s upper torso, ideal anchor points should not be further back than 200 mm [8”] from back of user’s seat.

In the event that the anchor points are further towards the rear of the vehicle [e.g. using a roll cage bar for wrap around attachment] the distance between the strap anchor points will narrow or even cross over as described in following graphs and tables.

· It is especially crucial to follow this strap routing when HANS® is in use.

The FIA Apendix J article 253 presently says up to 45 degrees below horizontal is the limit but 10 is recommended and just to keep things muddy the FIA published a Hans installation guide http://www.fiainstitute.com/publication ... _Guide.pdf that shows 0-20 degrees.

I believe everyone is headed toward 0-20 degrees referenced to horizontal with a 10 degree target, H&NR or not. So if you are building or modifying the seat/cage/restraints now, follow the 10 degree and you should be good to the current thinking for a while.

[walterclark]

The center of the bar is almost at the top of the openings, my shoulders are taller than the harness openings in the seat. My seat more or less sits on the ground.

Then it should be about perfect.

What do people recommend about the node in main hoop? From what I gather people generally either use saddle gussets are tube with plate over it. My notcher cant notch a short enough piece of tube to make gussets between the harness bars and the X. The angles also arent 90s or 45s so it makes buying a premade saddle gusset difficult.

You do not have to gusset the X at the sides, you may do it at the top and bottom, thus getting away from very short spans problem. The FIA rules on which most of this is based requires the junction of the main hoop diagonals be gusseted but says nothing about gusseting the harness bar since it is not considered a brace to the hoop. If you want to gusset around the harness bars, you could make a pair of taco style gussets for the sides of the X then split and notch them to fit around the harness bars, then weld them on and back together.

[Number_5]

Got my interest. Is it possible to be too tall for the openings in the seat?
John M